1. Field of the Invention
This invention relates to a decorative aquarium, and particularly to a water tight plug, which can provide a buffer effect for ambient temperature variation.
2. Description of the Prior Art
A conventional aquarium usually comprises a glass bowl with neck portion on the bottom thereof, and a watertight plug having a positioning ring. The watertight plug is mounted in the neck portion of the glass bowl by means of the positioning ring and a ring flange; the water in the glass bowl is isolated from the atmosphere completely. The decorative aquarium is usually mounted in a round hole of a decorative body by means of the neck portion of the glass bowl, and silicone is used to glue them together. The bottom of the decorative body usually has a music assembly so as to provide visual and listening pleasure.
In the conventional decorative aquarium, the glass bowl and the watertight plug are put into the water before being assembled together so as to remove air from the glass bowl. The watertight plug and the decorations therein have no air bubbles attached. After the neck portion of the glass bowl and the watertight plug are connected together, water cannot leak out because the watertight plug being is made of a resilient and sealing material. The inside of the glass bowl has no air left. However, variable ambient temperature may cause the pressure inside the glass bowl to vary; in the event of the increasing or decreasing pressure being higher than the connection and sealing force between the glass bowl and the watertight plug, the water in the glass bowl may leak out, or air might be sucked in to cause an air chamber to exist in the glass bowl.
In the conventional decorative aquarium, the flat portion on the watertight plug has a plurality of grooves which are made of a thinner material so as to allow for the expansion or shrinkage effect under different temperatures. However, the expansion tolerance of the flat portion of the groove is limited; it can only improve the problem of a conventional aquarium to some extent without solving such problem completely.